There is conventionally known that when data is transmitted and received between LSIs (Large Scale Integration), the transmission-side LSI transfers data via a data transfer line to the reception-side LSI and the reception-side LSI receives the data.
When data is transmitted and received between such LSIs, a reception timing or impedance of parallel data changes due to a data transmission/reception frequency, reception situation or substrate heat, and reception data may not be correctly received. Thus, the data transmission/reception is interrupted to make a reception adjustment at a constant period in order to keep an optimum reception state in the reception-side LSI. For example, for the reception adjustment, the transmission-side LSI transfers a specific pattern to the reception-side LSI thereby to adjust a reception timing or impedance.
A structure of the transmission-side LSI and the reception-side LSI will be described herein with reference to FIG. 32. As illustrated in FIG. 32, four data transmission signal lines that transmit data are connected between the transmission-side LSI and the reception-side LSI and a clock signal line that transmits a clock indicating a data reception timing is connected therebetween.
The transmission-side LSI includes a transmission data control unit that performs handshaking for data transfer and reception adjustment, a transmission data generation unit that generates transmission data, an adjustment data generation unit that generates adjustment data, and a parallel data transmission unit that transmits the transmission data and the adjustment data. The reception-side LSI includes a reception data control unit that performs handshaking, a reception end that receives data or clocks, a parallel data reception unit that receives data from the reception end in parallel, a reception data use unit that uses reception data, and a reception adjustment unit that makes a reception adjustment from adjustment data.
Data transmission/reception processing and reception adjustment processing in the transmission-side LSI and the reception-side LSI will be described herein with reference to FIG. 33. As illustrated in FIG. 33, the transmission-side LSI and the reception-side LSI start to transfer data when a device power supply is powered ON, and perform initialization between the transmission-side LSI and the reception-side LSI (step S1). Then, data is transmitted and received in a normal mode (step S2).
The reception-side LSI monitors a reception state and determines whether reception adjustment is necessary (step S3). Consequently, when it is determined that reception adjustment is necessary, the data transmission/reception is interrupted to proceed to an adjustment mode (step S4), and when the adjustment is completed (step S5), returns to the normal mode to restart the data transmission/reception.
The processing in the normal mode and the adjustment mode will be specifically described herein. At first, in the normal mode, the transmission-side LSI and the reception-side LSI perform handshaking in order to transfer data, and then the transmission-side LSI transmits data to the reception-side LSI via the data transmission signal lines as illustrated in FIG. 34.
In the adjustment mode, after the data transmission/reception is interrupted, the transmission-side LSI and the reception-side LSI perform handshaking for reception adjustment, and then the transmission-side LSI transmits an adjustment pattern to the reception-side LSI via the data transfer signal lines as illustrated in FIG. 35. Then, the reception-side LSI uses the adjustment pattern to make a reception adjustment. Thereafter, the reception-side LSI finishes the reception adjustment and then returns to the normal mode. In this way, in the data transmission processing between the transmission-side LSI and the reception-side LSI, the normal mode and the adjustment pattern are alternately switched as illustrated in FIG. 36.    Patent Literature 1: Japanese Laid-open Patent Publication No. 04-162840
However, the above method that interrupts data transmission/reception to make a reception adjustment performs data transmission/reception and makes a reception adjustment at different timings, and thus had a problem that a data transmission efficiency lowers. That is, in order to make a reception adjustment, transmission/reception is temporarily interrupted while data is being transmitted and received, and then a reception adjustment is made, and thus a data transmission efficiency lowers.